Modern simple cycle gas turbines have thermal efficiency of 33-37%, but much better utilization of fuel availability is possible, because their exhaust gases have a high temperature exceeding 500.degree. C. Thermodynamic calculations prove that, by using exhaust gases temperature potential, power output and thermal efficiency of power systems with gas turbines may be doubled in the ideal, theoretical case. Practically, gas turbine waste heat is utilized for power production in a bottoming Rankine cycle engine usually using water as a working fluid (see, H. Cohen, G. F. C. Rogers, and H. I. H. Saravanamuttoo, "Gas Turbine Theory", 3rd edition, Longman, Harlow, UK, 1987; and J. H. Horlock, "Combined Power Plants", Pergamon Press, Oxford-New York-Seoul-Tokyo, 1992). Combined cycle plants employing gas turbine and Rankine bottoming cycle steam engine are widely applied in energetics ensuring high thermal efficiency and moderate capital cost of the power system. Bottoming Rankine cycle steam engine is a complicated closed cycle system with high pressure in a boiler and vacuum in a condenser. This engine is quite similar to base load power steam plants applied in energetics. It includes machine equipment (steam turbines, high pressure feedwater pumps and vacuum pumps); several heat exchangers ensuring heat transfer from gas turbine exhaust gases to the boiling high pressure water and steam, and heat transfer from low pressure steam to ambient (boilers, condenser, steam and water heaters), water treatment system that ensures conditioning of the working fluid, cooling water system or cooling air system etc. Since an average specific capital cost of a gas turbine is 350 $/kW only, capital cost of the bottoming Rankine cycle equipment is 1,000-1,200 $ for 1 kW of the bottoming cycle capacity, that is high enough and is close to numbers valid for base load steam plants (see, H. G. Stoll and others, "Least-Cost Electric Utility Planning", John Wiley & Sons, New York, 1989).
The bottoming Rankine cycle steam engine cannot ensure quick response on a load change. It means, that combined cycle plant may be applied for base load only.
Gas turbine power output and thermal efficiency drop when density of inlet air decreases. Therefore increasing atmospheric air temperature and decreasing its pressure lead to degradation of gas turbine characteristics. To avoid this, various methods of cooling air, entering gas turbine compressor, are proposed. They apply evaporative cooling or separate refrigerating machines that may be combined with an accumulator of cold (see, H. Shreiber, "Using Ice Storage to Enhance Gas Turbine Capacity", EPRI Journal, October-November 1991; H. Jericha, F. Holler, "Modular Combined Cycle Plant Enhanced for More Efficiency, Power and Maintainability", 1991 ASME COGEN-TURBO IGTI, v. 6, pp. 403-410; and "Inlet Cooling at 100.degree. F. and Higher", Gas Turbine World, May-June 1993).
Evaporative cooling of inlet air is not efficient and can be used only when atmospheric air humidity is low. Refrigerating machines ensure deep cooling of inlet air, but these devices are separate units that consume electric power from the grid and are simply added to existing gas turbine equipment. Complexity of refrigerating machines, their environmental impact, high capital and operational costs are additional factors that should be taken into account. Refrigerating machinery is a source of additional problems in operation and maintenance of gas turbine power system.